5. How would you use information that we have learned over the last two lessons to revise our working model to explain how fuel makes a car engine work (and therefore a car move)? Use the diagram below to help you verbally describe any changes you would make. 3. **** Image Source d a mm/ Iaptryrn SA Dlistthom
The explanations of diagrams are as follows:
The diagrams shown are the of 4 stroke petrol engine. There are a total of four processes by which the chemical energy of the fuel is used to convert into heat energy and that heat energy is used to convert into mechanical energy required for the motion of a vehicle. The four processes are as follows:
1. Suction- At this stage as shown in the figure-1 piston inside the cylinder moves from the top dead center to the bottom dead center. When the motion of the piston starts from the top dead center the inlet valve (Right side) opens and fuel starts admitting inside the cylinder. As the piston starts moving upwards the inlet valve closes.
2. Compression- As the piston moves upwards from the bottom dead center to towards the top dead center the fuel admitted inside the cylinder is compressed. When the piston reaches the top dead center a spark is generated and the fuel which is at high pressure and temperature due to compression burnout produces gasses that push the piston down in the cylinder (Figure-2).
3. expansion or power stroke- The downward motion of the piston provides the required mechanical energy which is required to move the vehicle. This energy is transferred to the crankshaft and then to the wheels with the help of a transmission mechanism (Figure-3).
4. Exhaust- As shown in figure-4 after expansion stroke the piston starts moving up and at the same time the outlet valve( left side) open up. All the combustion products after providing their energy to the piston go outside to the atmospehere. The process will remain to continue till the piston inside the cylinder reaches the top dead center.
After this, the process repeated again and the power keep on generating inside the cylinder to propel the vehicle.
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